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The medication is called Bravecto. It's a dog chew so powerful that one dose can kill fleas and ticks for three months. Pharmaceutical giant Merck says it's safe and effective, but the number of dog owners who think otherwise is growing.

White's dog, JoJo, vomited the first two times she gave him Bravecto, which is a known side effect. But 12 hours after the third dose, he had to be rushed to the veterinarian for emergency CPR. It didn't work and JoJo died.

"It was the worst day of my life," White said.

Chris Weber says his dog, Truck, suffered for weeks after dose number three. Then one day, "He put his head in the bowl, turned back and looked at me and collapsed at my feet," Weber told Strickland.

Patti Mastric told Strickland her dog, Duncan, had a fatal reaction to his first dose of Bravecto. And within hours, she said, her second dog, Trey, had a seizure after getting the pill.

"We'd just lost our one dog, and our other dog is just in front of us, going to pieces," Mastric said.

Mastric says Trey now has less energy. She can't prove Bravecto was the cause, but she believes it was.

"It couldn't have been anything else," Mastric said.

Mastric is administrator of a Facebook page with more than 30,000 members.

Posts from around the globe document death and suspicion.

An FDA report Strickland obtained has tallied 355 suspected deaths since the pill's release in 2014.

"We're seeing some of these dogs that just seem to crash for lack of a better word," said Pennsylvania veterinarian Elizabeth Carney.

She has asked the FDA to add a seizure warning to Bravecto's label.

"I think it's more important to try to figure out what's going on,” she said.

Merck declined Strickland's request for an on-camera interview. In an email to Strickland, a Merck spokesperson said the company has dispensed 34 million doses and that reports of serious adverse events are very rare, less than .01 percent.